In today's semiconductor manufacturing industry, it is important to manufacture semiconductor devices as quickly and efficiently as possible and it is equally important to utilize resources in the production area most efficiently in order to meet business needs and customer deadlines. To gain competitive advantage, a semiconductor manufacturing fabrication plant is continuously looking for opportunities to shorten cycle time, reduce costs, decrease variability, increase productivity, and to ensure on-time delivery of customer orders. As such, it is undesirable for production lots, i.e. groups of substrates processed together as a group, to sit around idle while awaiting processing. It is also important to utilize the various production and metrology tools so that they are being used efficiently and to their maximum capacity. When a production tool is idle, or when a lot of substrates sits idle, cycle time is increased, costs increase, and productivity decreases. The manufacturing facility runs inefficiently and it is therefore more difficult or even impossible to ensure on-time delivery of customer orders.
It is also important to meet customer deadlines, maintain line balance and avoid inventory accumulation. More particularly, it is undesirable to have inventory accumulating at a particular location or manufacturing tool, while other manufacturing tools sit idle. It is also important for production personnel to process the work pieces, i.e. “lots,” in the order that most efficiently achieves the above-identified objectives. As a corollary, it is important for production personnel to quickly and correctly identify which production lots to process, to achieve these objectives.